Enceladus-3 (March 12, 2008) Options

[Guest_AlexBlackwell_*]

Excerpt from Cassini Significant Events for 02/16/06 - 02/22/06:

"As mentioned in previous weeks, the project has been working on adopting a new reference trajectory in order to raise the minimum Titan flyby altitude for various encounters. Today the project reached a decision to proceed with the 'optocc2' trajectory. Additional work is still to be performed before delivery of the final files. This will include minor tweaks that have been analyzed in other trajectories, adjusting orbit 68 timing, and capture of an Enceladus plume occultation on orbit 28."

For the record, the new reference trajectory will result in an even more spectacular Enceladus-3 flyby [61EN (t) E3] on March 12, 2008.

[Guest_BruceMoomaw_*]

It was casually confirmed in one of the new EGU abstracts that Cassini's extended mission will include an attempt to determine Enceladus' quadrupole gravitational field -- which should tell us vastly more about its internal mass distribution, and thus about what really IS going on in its innards (which seems at this point to be the single biggest mystery unearthed by Cassini):

http://www.cosis.net/abstracts/EGU06/05029/EGU06-J-05029.pdf

[volcanopele]

Even though the encounter distance is closer, don't expect too much better imaging. We come in at high-phase, C/A is over the night side, and Enceladus goes into eclipse 3 min. after C/A.

[Guest_AlexBlackwell_*]

Even though the encounter distance is closer, don't expect too much better imaging. We come in at high-phase, C/A is over the night side, and Enceladus goes into eclipse 3 min. after C/A.

Just out of curiosity, and assuming the geometry was favorable, how much pixel smear would ISS expect at the new 25 km C/A altitude?

[Holder of the Tw...]

Even though the encounter distance is closer, don't expect too much better imaging. We come in at high-phase, C/A is over the night side, and Enceladus goes into eclipse 3 min. after C/A.

Any chance at all that they can snap off some pictures of the south pole before Enceladus goes into shadow?

[ljk4-1]

Check this out:

http://drudgereport.com/flash8na.htm

[volcanopele]

Check this out:

http://drudgereport.com/flash8na.htm

Unfortunately, the distance for E3 quoted is the distance to the center of enceladus for the old flyby altitude. The old altitude was 100 km, now it is much lower.

[Guest_AlexBlackwell_*]

Unfortunately, the distance for E3 quoted is the distance to the center of enceladus for the old flyby altitude. The old altitude was 100 km, now it is 25 km.

I guess no one has leaked Drudge the new reference trajectory recommendations

[Guest_BruceMoomaw_*]

TWENTY-FIVE KM?!! You guys are really taking this place seriously, aren't you? I hope the navigation is better than that on MCO...

In that connection, one catastrophe that has yet to strike the US space program is the failure of an long, expensive outer Solar System mission just before its arrival. What will the public and Congressional reaction be when that finally happens? It looked as though it might happen with Galileo, but JPL succeeded (to their unquestionable credit) in pulling enough chestnuts out of the fire to remove that impression in that case.

At the risk of setting off the dog (aka Alex) again: I mentioned this point to Spilker's subgroup on Europa lander design at the Europa Focus Group Workshop, and got an enthusiastic response from JPL's Karla Clark -- we do NOT want something as expensive and long-term as a Europa Astrobiology Lander to fail at the very moment it's trying to land on Europa, and for that reason the best role for a little piggyback lander attached to Europa Orbiter may well be to check out the engineering characteristics of Europa's surface rather than carrying out any specifically scientific studies.

[ugordan]

TWENTY-FIVE KM?!! You guys are really taking this place seriously, aren't you? I hope the navigation is better than that on MCO...

I'm wondering about this figure as well, I noticed volcanopele edited it out of his post. Does that figure really hold in the new updated trajectory?
That has got to be the fastest and closest approach by any mission so far!
I hope Enceladus doesn't grow any really tall mountains in the meantime

What exactly is the scientific justification of such a dangerously close pass?

[Guest_AlexBlackwell_*]

...JPL's Karla Clark -- we do NOT want something as expensive and long-term as a Europa Astrobiology Lander to fail at the very moment it's trying to land on Europa...

Now that's a visionary statement.

I'm wondering about this figure as well, I noticed volcanopele edited it out of his post. Does that figure really hold in the new updated trajectory?

"Officially," the new reference trajectory is still in review at the Project/Program level; a decision should be forthcoming very shortly. I won't speak for Jason, but unofficially, the 25 km figure is the new Enceladus-3 flyby C/A altitude under all options that were being considered.

What exactly is the scientific justification of such a dangerously close pass?

More on that later; however, sooner than 2008

[volcanopele]

Technically, that number is official (well, it isn't going to change). As the Sig. events report suggest, a few additional tweaks are planned, but nothing that will effect Enceladus-3.

[Guest_AlexBlackwell_*]

Technically, that number is official (well, it isn't going to change).

I meant officially released. As you note, though, it's not going to change, especially since that C/A altitude was the same under all options. And I am heartened that the new reference trajectory helps out RSS, too

[The Messenger]

TWENTY-FIVE KM?!! You guys are really taking this place seriously, aren't you? I hope the navigation is better than that on MCO...

In that connection, one catastrophe that has yet to strike the US space program is the failure of an long, expensive outer Solar System mission just before its arrival. What will the public and Congressional reaction be when that finally happens? It looked as though it might happen with Galileo, but JPL succeeded (to their unquestionable credit) in pulling enough chestnuts out of the fire to remove that impression in that case.

At the risk of setting off the dog (aka Alex) again: I mentioned this point to Spilker's subgroup on Europa lander design at the Europa Focus Group Workshop, and got an enthusiastic response from JPL's Karla Clark -- we do NOT want something as expensive and long-term as a Europa Astrobiology Lander to fail at the very moment it's trying to land on Europa, and for that reason the best role for a little piggyback lander attached to Europa Orbiter may well be to check out the engineering characteristics of Europa's surface rather than carrying out any specifically scientific studies.

I agree - 25km is much too close. I suggest that they take a good hard look at what happens in the 950km pass of Titan in July, before cutting the number in stone. There is clearly an atmospheric hazard that we cannot be at all certain about.

[ugordan]

I agree - 25km is much too close. I suggest that they take a good hard look at what happens in the 950km pass of Titan in July, before cutting the number in stone. There is clearly an atmospheric hazard that we cannot be at all certain about.

You can't compare apples and oranges. What happens at Titan hardly suggests anything about Enceladus. Besides, the C/A distance will probably not be above the south pole where the plumes originate.
Personally, I'm not afraid of the plumes as much as I am of delivery errors. I do want to see an extended mission!

Then again, the navigation team probably knows what they're doing by now.